The present invention relates to a fuel preheater system. More particularly, the present invention relates to a system which heats engine coolant and uses the engine coolant to heat fuel prior to combustion of the fuel in a vehicle engine.
Vehicles using diesel fuel have long experienced fuel systems problems during cold weather operation. At sufficiently low temperatures, diesel fuel becomes undesirably viscous, a condition which is exacerbated by the formation of wax crystals in the fuel. Cold diesel fuel thus may clog a fuel filter, possibly interrupting the operation of the vehicle or preventing starting.
It is therefore desirable to provide a system for preheating fuel prior to its introduction to a fuel filter. Such a system must be sized for easy installation on a vehicle and must be rugged enough to withstand the jarring and vibration typically encountered during vehicle operation.
It has been recognized that a fuel preheater system preferably makes use of fluids already circulating in the vehicle engine as opposed to auxiliary fuel supplies for use as the working fluid for heating the fuel. Preheater systems operating on auxiliary fuel supplies such as propane gas or butane gas pose unacceptable risks of explosion. Conveniently, a portion of the fuel itself might be used to provide heat to the main supply of fuel. Alternatively, the engine coolant might be used.
According to the present invention, an apparatus is provided for preheating fuel from a vehicle fuel tank prior to feeding the fuel to a vehicle engine. The apparatus comprises first heat exchange means for using fuel from the fuel tank to heat engine coolant received from the vehicle engine, and second heat exchange means for using engine coolant discharged from the first heat exchange means to heat fuel received from the fuel tank. The first heat exchange means includes means for burning fuel received from the fuel tank to form a combustion product stream. The first heat exchange means also includes first passageway means for passing engine coolant in counterflow heat exchange relationship with a combustion product stream to heat the engine coolant to a predetermined temperature.
The present invention also relates to a method for preheating fuel from a vehicle fuel tank for feeding to a vehicle engine. The method comprises the steps of feeding a first portion of the fuel from the fuel tank to a first heat exchanger, and burning the portion of fuel in the first exchanger to form a combustion product stream. The method further comprises the steps of feeding a first stream of engine coolant from the vehicle engine to the first heat exchanger, passing the combustion products stream in heat exchange relationship with the first engine coolant stream in the first heat exchanger to heat the engine coolant stream to a predetermined temperature to form a heated engine coolant stream, and feeding a second portion of fuel from the fuel tank to the second heat exchanger. The method further comprises the steps of feeding the heated engine coolant stream to the second heat exchanger and passing the second portion of fuel in heat exchange relationship with a heated engine coolant stream in the second heat exchanger to heat the second portion of fuel to a predetermined temperature.
Advantageously, the present system makes use of both engine coolant and a portion of the fuel itself to provide heat exchange in a pair of cooperating heat exchangers.
Further advantageously, the system can optionally include a heat exchanger which can be easily rendered inoperable by a user, for example, in warm weather conditions.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.